Electroreflectance and Band Structure ofGaxIn1−xPAlloys

The electroreflectance spectra of solution-grown ${\mathrm{Ga}}_x{\mathrm{In}}_{1-x}\mathrm{P}$ alloys were measured at room temperature in the whole range of composition. The variation of the $E_0$, $E_1$, $E_0^{\prime }$, and $E_2$ energies with concentration is reported: It is parabolic for $E_0$ and $E_1$, and approximately linear for $E_0^{\prime }$ and $E_2$. Except for $E_1$ these results agree with the calculation of the band structure by the dielectric two-band method in the virtual-crystal approximation including the effect of disorder. The latter effect is found small. For $E_1$ the deviation from a linear variation is larger than calculated. $E_1$ exhibits another interesting anomaly: Its spin-orbit splitting is maximum for $x=0.5\mathrm{}$. The $\overrightarrow{\mathrm{k}}·\overrightarrow{\mathrm{p}}$ method is used to calculate some band parameters from our data. The $\Gamma -X$ conduction-band crossover energy $E_c$ and composition $x_c$ are accurately determined using the $E_0$ vs $x$ curve and the indirect gaps obtained from optical absorption. $x_c=0.63\mathrm{}\pm 0.015$, $E_c=2.14\mathrm{}\pm 0.01$ eV.